Cushing's disease: adrenal steroidogenesis inhibitors

Medical Therapy of Endogenous Cushing's Syndrome with Steroidogenesis Inhibitors: Treatment Rationale, Available Drugs, and Therapeutic Effects

Endogenous Cushing's syndrome (CS) is a rare disease characterized by a glucocorticoid excess. If inadequately treated, hypercortisolism can lead to increased morbidity and mortality. Surgical removal of the underlying tumor is the first-line treatment but is sometimes not feasible or even contraindicated. Additionally, in cases with severe CS, rapid control of hypercortisolism may be required. In these scenarios, steroidogenesis inhibitors represent a therapeutic alternative to surgery. Over the last years, the knowledge of the broad therapeutic effects of steroidogenesis inhibitors per se and the number of available drugs have increased. However, large comparative studies are still lacking. Accordingly, the decision on which drug to be used in a certain patient or clinical setting may be difficult. This review aims to summarize the main characteristics of steroidogenesis inhibitors.

Targeted analysis of Ubiquitin-Specific Peptidase (USP8) in a population of Iranian people with Cushing's disease and a systematic review of the literature

OBJECTIVE

Activating mutation in Ubiquitin-specific peptidase (USP8) is identified to enhance cell proliferation and adrenocorticotropic hormone (ACTH) secretion from corticotroph pituitary adenoma. We investigated the USP8 variant status in a population of Iranian people with functional corticotroph pituitary adenoma (FCPA). Moreover, a systematic review was conducted to thoroughly explore the role of USP8 variants and the related pathways in corticotroph adenomas, genotype-phenotype correlation in USP8-mutated individuals with FCPA, and the potential role of USP8 and epidermal growth factor receptor (EGFR) as targeted therapies in PFCAs.

METHODS

Genetic analysis of 20 tissue samples from 19 patients with PFCAs was performed using Sanger sequencing. Moreover, a systematic literature review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Scopus, web of Sciences, and Cochrane databases were searched. The last search was performed on 20 September 2023 for all databases.

RESULTS

In our series, we found two somatic mutations including a 7-bp deletion variant: c.2151_2157delCTCCTCC, p. Ser718GlnfsTer3, and a missense variant: c.2159 C > G, p. Pro720Arg (rs672601311) in exon 14. The Systematic review indicated USP8 variant in 35% of corticotroph adenomas, with the highest frequency (25%) in 720 code regions, p. Pro720Arg. Data regarding the impact of USP8 mutational status on clinical characteristics and outcomes in FCPAs are inconsistent. Moreover, Pasireotide as well as inhibitors of EGFR such as Gefitinib and Lapatinib, as well as USP8 inhibitors including -ehtyloxyimino9H-indeno (1, 2-b) pyrazine-2, 3-dicarbonitrile, DUBs-IN-2, and RA-9 indicated promising results in treatment of corticotroph adenomas.

CONCLUSION

Although the USP8-EGFR system has been identified as the main trigger and target of corticotroph tumorigenesis, more precise multicenter studies are required to yield more consistent information regarding the phenotype-genotype correlation and to develop effective targeted therapies.

Osilodrostat: A Novel Potent Inhibitor of 11-Beta-Hydroxylase for the Treatment of Cushing's Syndrome

Osilodrostat is a novel potent oral steroidogenesis inhibitor with a non-steroidal chemical structure, recently approved for the treatment of adult patients with endogenous Cushing's syndrome, and Cushing's disease not cured bytab pituitary surgery or in whom pituitary surgery is not an option. Osilodrostat has been evaluated in different multicentre phase II and III clinical studies, and has shown to have notable effects, such as significant reductions in cortisol secretion, associated with significant improvement in body weight, blood pressure, glucose metabolism, lipid profile, psychological status and quality of life. The favourable safety profile, combined with the relevant efficacy, could make osilodrostat suitable as medical treatment in several phases of the Cushing's syndrome treatment journey: before surgery, as preoperative treatment, or instead of surgery, in cases where surgery is not an option or refused, as first-line treatment; after surgery, in cases of persistent or recurrent disease, as second-line treatment; after second surgery or radiotherapy following pituitary surgery as bridging treatment waiting for the definitive disease control, as third-line treatment. Further real-world clinical experience data are needed to confirm the current knowledge.

Seliciclib: A New Treatment for Cushing's Disease?

Previous studies have suggested that corticotroph tumours are associated with the overexpression of cyclin E and that the inactivation of cyclin-dependent kinases, which activate cyclin E, may have antisecretory and antiproliferative effects. Seliciclib, also known as R-roscovitine, is a pituitary-targeting agent shown to inhibit the growth of corticotroph tumour cells via cyclin E and retinoblastoma protein-mediated pathways. A recent study investigated the role of seliciclib in regulating biochemical parameters in a small number of patients with Cushing's disease, providing preliminary data on its possible therapeutic effectiveness in treating this disorder.

Iatrogenic adrenal insufficiency in adults

Iatrogenic adrenal insufficiency (IAI) is the most common form of adrenal insufficiency in adult patients, although its overall exact prevalence remains unclear. IAI is associated with adverse clinical outcomes, including adrenal crisis, impaired quality of life and increased mortality; therefore, it is imperative that clinicians maintain a high index of suspicion in patients at risk of IAI to facilitate timely diagnosis and appropriate management. Herein, we review the major causes, clinical consequences, diagnosis and care of patients with IAI. The management of IAI, particularly glucocorticoid-induced (or tertiary) adrenal insufficiency, can be particularly challenging, and the provision of adequate glucocorticoid replacement must be balanced against minimizing the cardiometabolic effects of excess glucocorticoid exposure and optimizing recovery of the hypothalamic-pituitary-adrenal axis. We review current treatment strategies and their limitations and discuss developments in optimizing treatment of IAI. This comprehensive Review aims to aid clinicians in identifying who is at risk of IAI, how to approach screening of at-risk populations and how to treat patients with IAI, with a focus on emergency management and prevention of an adrenal crisis.

Current and Emerging Pharmacological Therapies for Cushing's Disease

Cushing's Disease (CD), hypercortisolism due to pituitary ACTH secreting neuroendocrine neoplasm, is associated with increased morbidity and, if untreated, mortality in about half of the affected individuals. Consequently, the timely initiation of effective treatment is mandatory. Neurosurgery is the first line and the only potentially curative treatment; however, 30% of patients will have persistent disease post-surgery. Furthermore, a small percentage of those initially controlled will develop hypercortisolism during long-term follow- up. Therefore, patients with persistent or recurrent disease, as well as those considered non-eligible for surgery, will need a second-line therapeutic approach, i.e., pharmacotherapy. Radiation therapy is reserved as a third-line therapeutic option due to its slower onset of action and its unfavorable profile regarding complications. During the past few years, the understanding of molecular mechanisms implicated in the physiology of the hypothalamus-pituitary-adrenal axis has evolved, and new therapeutic targets for CD have emerged. In the present review, currently available treatments, compounds currently tested in ongoing clinical trials, and interesting, potentially new targets emerging from unraveling molecular mechanisms involved in the pathophysiology of Cushing's disease are discussed.

Cushing's syndrome

Endogenous Cushing's syndrome results from excess glucocorticoid secretion, which leads to a myriad of clinical manifestations, comorbidities, and increased mortality despite treatment. Molecular mechanisms and genetic alterations associated with different causes of Cushing's syndrome have been described in the last decade. Imaging modalities and biochemical testing have evolved; however, both the diagnosis and management of Cushing's syndrome remain challenging. Surgery is the preferred treatment for all causes, but medical therapy has markedly advanced, with new drug options becoming available. Nevertheless, several comorbidities remain even after patient remission, which can affect quality of life. Accurate and timely diagnosis and treatment are essential for mitigating chronic complications of excess glucocorticoids and improving patient quality of life. In this Seminar, we aim to update several important aspects of diagnosis, complications, and treatment of endogenous Cushing's syndrome of all causes.

Cushing's Disease: Long-Term Effectiveness and Safety of Osilodrostat in a Polish Group of Patients with Persistent Hypercortisolemia in the Experience of a Single Center

Osilodrostat is a potent oral steroidogenesis inhibitor that has emerged as the new medical agent for patients with Cushing's disease (CD) requiring long-term medical therapy for hypercortisolemia control. Its efficacy and safety have been assessed in clinical trials; however, real-world evidence is still scarce. This study aimed to investigate the long-term treatment (156 weeks) clinical and biochemical effect of osilodrostat in six patients with CD at a single center in Poland, initially participating in the LINC4 study. At week 36, all six patients met the key secondary endpoint of the LINC4 trial, achieving normalization of median urinary free cortisol. Osilodrostat treatment allowed for complete disease control in all patients and none of the patients was excluded due to the lack of treatment effectiveness in 156 weeks of follow-up. All patients demonstrated significant improvement from baseline on most metabolic and cardiovascular parameters, which was most evident at week 36 and sustained throughout the study period. This study supports and strengthens the role of osilodrostat as an effective long-term medical treatment in patients with CD. We also present three patient case histories in detail to highlight the clinical situations that endocrinologists might face during osilodrostat therapy.

An individualized approach to the management of Cushing disease

Cushing disease caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary corticotroph adenoma leads to hypercortisolaemia with high mortality due to metabolic, cardiovascular, immunological, neurocognitive, haematological and infectious conditions. The disorder is challenging to diagnose because of its common and heterogenous presenting features and the biochemical pitfalls of testing levels of hormones in the hypothalamic-pituitary-adrenal axis. Several late-night salivary cortisol and 24-h urinary free cortisol tests are usually required as well as serum levels of cortisol after a dexamethasone suppression test. MRI might only identify an adenoma in 60-75% of patients and many adenomas are small. Therefore, inferior petrosal sinus sampling remains the gold standard for confirmation of ACTH secretion from a pituitary source. Initial treatment is usually transsphenoidal adenoma resection, but preoperative medical therapy is increasingly being used in some countries and regions. Other management approaches are required if Cushing disease persists or recurs following surgery, including medications to modulate ACTH or block cortisol secretion or actions, pituitary radiation, and/or bilateral adrenalectomy. All patients require lifelong surveillance for persistent comorbidities, clinical and biochemical recurrence, and treatment-related adverse effects (including development of treatment-associated hypopituitarism). In this Review, we discuss challenges in the management of Cushing disease in adults and provide information to guide clinicians when planning an integrated and individualized approach for each patient.

The potential role and mechanism of circRNA/miRNA axis in cholesterol synthesis

Cholesterol levels are an initiating risk factor for atherosclerosis. Many genes play a central role in cholesterol synthesis, including HMGCR, SQLE, HMGCS1, FDFT1, LSS, MVK, PMK, MVD, FDPS, CYP51, TM7SF2, LBR, MSMO1, NSDHL, HSD17B7, DHCR24, EBP, SC5D, DHCR7, IDI1/2. Especially, HMGCR, SQLE, FDFT1, LSS, FDPS, CYP51, and EBP are promising therapeutic targets for drug development due to many drugs have been approved and entered into clinical research by targeting these genes. However, new targets and drugs still need to be discovered. Interestingly, many small nucleic acid drugs and vaccines were approved for the market, including Inclisiran, Patisiran, Inotersen, Givosiran, Lumasiran, Nusinersen, Volanesorsen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen, Elasomeran, Tozinameran. However, these agents are all linear RNA agents. Circular RNAs (circRNAs) may have longer half-lives, higher stability, lower immunogenicity, lower production costs, and higher delivery efficiency than these agents due to their covalently closed structures. CircRNA agents are developed by several companies, including Orna Therapeutics, Laronde, and CirCode, Therorna. Many studies have shown that circRNAs regulate cholesterol synthesis by regulating HMGCR, SQLE, HMGCS1, ACS, YWHAG, PTEN, DHCR24, SREBP-2, and PMK expression. MiRNAs are essential for circRNA-mediated cholesterol biosynthesis. Notable, the phase II trial for inhibiting miR-122 with nucleic acid drugs has been completed. Suppressing HMGCR, SQLE, and miR-122 with circRNA_ABCA1, circ-PRKCH, circEZH2, circRNA-SCAP, and circFOXO3 are the promising therapeutic target for drug development, specifically the circFOXO3. This review focuses on the role and mechanism of the circRNA/miRNA axis in cholesterol synthesis in the hope of providing knowledge to identify new targets.

Clinical Utility of Osilodrostat in Cushing's Disease: Review of Currently Available Literature

Cushing's disease (CD) is caused by endogenous hypercortisolism as a result of adrenocorticotropin (ACTH) secretion from a pituitary tumor. The condition is associated with multiple comorbidities and increased mortality. First-line therapy for CD is pituitary surgery, performed by an experienced pituitary neurosurgeon. Hypercortisolism may often persist or recur after initial surgery. Patients with persistent or recurrent CD will generally benefit from medical therapy, often administered to patients who underwent radiation therapy to the sella and are awaiting its salutary effects. There are three groups of medications directed against CD, including pituitary-targeted medications that inhibit ACTH secretion from tumorous corticotroph cells, adrenally-directed medications that inhibit adrenal steroidogenesis and a glucocorticoid receptor (GR) antagonist. The focus of this review is osilodrostat, a steroidogenesis inhibitor. Osilodrostat (LCI699) was initially developed to lower serum aldosterone levels and control hypertension. However, it was soon realized that osilodrostat also inhibits 11-beta hydroxylase (CYP11B1), leading to a reduction in serum cortisol levels. The focus of drug development then shifted from treatment of hypertension to treatment of hypercortisolism in CD. In a series of studies (LINC 1 through 4), osilodrostat was shown to be effective in normalizing 24-h urinary free cortisol (UFC) in the majority of treated patients and was approved for patients with CD who have failed surgery or are not surgical candidates. Further study is needed to examine the role of combination therapy as well as long-term outcomes of treated patients. Osilodrostat was shown to have an overall good safety profile. Most common adverse effects include nausea, headache, fatigue, arthralgias, dizziness, prolonged QTc interval, hypokalemia. In females, the drug can cause hirsutism and acne. Osilodrostat is administered twice daily, making it a good choice for patients with difficulty adhering to more complex regimens. Osilodrostat has an important, albeit adjunctive, role in the management of patients with CD.

Unmet needs on the current medical management of Cushing's syndrome: results from a Delphi panel of Italian endocrinologists

BACKGROUND

Cushing's syndrome (CS) is a rare clinical condition caused by excessive cortisol secretion from adrenal glands. CS is associated with increased mortality and morbidity; therefore, a prompt diagnosis and an effective therapeutic approach are strongly necessary to improve the patient's clinical management. The first-line treatment for CS is surgery, while medical treatment has historically played a minor role. However, thanks to the availability of novel compounds, the possibility of improving hypercortisolism control using different drug combinations emerged.

PURPOSE

No absolute recommendations are available to guide the therapeutic choice for patients with CS and, consequently, the awareness of unmet needs in CS management is growing. Although new data from clinical trials are needed to better define the most appropriate management of CS, an expert consensus approach can help define unmet needs and optimize the current CS management and treatment.

METHODS

Twenty-seven endocrinologists from 12 Italian regions, working among the main Italian referral centers for hospital endocrinology where they take care of CS patients, were involved in a consensus process and used the Delphi method to reach an agreement on 24 statements about managing CS patients.

RESULTS

In total, 18 statements reached a consensus. Some relevant unmet needs in the management of CS were reported, mainly related to the lack of a pharmacological treatment successful for the majority of patients.

CONCLUSION

While acknowledging the difficulty in achieving complete disease control, a significant change in CS management requires the availability of medical treatment with improved efficacy and safety over available therapeutic options at the time of the current study.

LC-MS/MS method for simultaneous quantification of osilodrostat and metyrapone in human plasma from patients treated for Cushing's Syndrome

Steroidogenesis inhibitors such as metyrapone (MTP) and osilodrostat (ODT) have a key role in the medical treatment of endogenous Cushing's Syndrome (ECS). Both drugs are characterized by a high inter-individual variability of response and require a dose-titration period to achieve optimal control of cortisol excess. However, PK/PD data remain scarce for both molecules and a pharmacokinetically guided approach could help reaching eucortisolism more rapidly. We aimed to develop and validate a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of ODT and MTP in human plasma. After addition of isotopically labeled internal standard (IS), plasma pretreatment consisted in protein precipitation with acetonitrile including 1% formic acid (v/v). Chromatographic separation was performed on Kinetex® HILIC (4.6 × 50 mm; 2.6 µm) analytical column with an isocratic elution during the 2.0-min run time. The method was linear from 0.5 to 250 ng/mL for ODT and from 2.5 to 1250 ng/mL for MTP. Intra- and inter-assay precisions were < 7.2%, with an accuracy ranging from 95.9% to 114.9%. The IS-normalized matrix effect ranged from 106.0% to 123.0% (ODT) and from 107.0% to 123.0% (MTP) and the range of the IS-normalized extraction recovery was 84.0-101.0% for ODT and 87.0-101.0% for MTP. The LC-MS/MS method was successfully applied in patients' plasma samples (n = 36), trough concentration of ODT and MTP ranged from 2.7 ng/mL to 8.2 ng/mL and from 10.8 ng/mL to 27.8 ng/mL, respectively. Incurred sample reanalysis exhibits less than 14% difference between the first and the second analysis for both drugs. This accurate and precise method, meeting all validation criteria, can therefore be used for plasma drug monitoring of ODT and MTP within the dose-titration period.